The battle of Qadesiya was a decisive victory for the Muslim Arabs in 14 AH in the time of Caliph Omar. Qadesiya was a small village by Euphrates near Kufa. In this battle, the famous Iranian flag was lost which was a great dishonor for the Iranian army. Until this time the Arab invaders were not taken seriously and the king Yazdgerd 3 did not show characteristics necessary to lead the Sassanid Empire. The battle of Qadesiya lasted for four days. At the end of the first day, the Iranian army repelled Arabs with the use of elephants. The second day, the tables turned and arrows blinded many of the elephants; another army arriving from Syria helped stop the Persian army. The battle went on during the third day and continued through the night when the Caliph forces attacked the Iranian camp at night. Day 4, started with a sandstorm blowing from behind the Arab invaders which completely paralyzed the Persian army. Rostam Farrokhzad, the Iranian commander was killed and the Persian army totally disintegrated.After this battle, the Arabs migrated from the Arab Peninsula towards Mesopotamia and settled in today's Iraq. Other Iranian cities were then taken gradually and Muslim conquest of Persia continued for almost 100 years.The size of the Persian army in Qadesiya has been highly exaggerated and accounts of historians including dates and numbers just do not fit in. There's only one certainty, that is: Iranians have carried a dislike against Omar ever since and probably that is one basis for Iranians accepting the Shiite sect of Islam which does not recognize the first 3 caliphs after prophet Mohammad passed away.